Gas turbine engines are used to power aircraft, watercraft, power generators, pumps and the like. Turbofan gas turbine engines typically include a fan, a compressor, a combustor, and a turbine. Conventionally, rotor stages included in such engines comprise a plurality of radially extending blades mounted on a disc. The blades are mounted on the disc by inserting a root portion of the blade in a complementary retention groove in the outer face of a disc periphery.
In some engines, to ensure a radially smooth inner surface for air to flow over as it passes through a rotor stage, annulus fillers can be used to bridge the spaces between adjacent fan blades. The annulus fillers may be manufactured from relatively lightweight materials and, in the event of damage, may be replaced independently of the blades.